Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$238.61	3.535%	$247.0449	$247.04	$247.05	$247.00
Purchase #2	$52.49	13.478%	$59.5646	$59.56	$59.55	$59.60
Purchase #3	$52.25	5.500%	$55.1238	$55.12	$55.10	$55.10
Purchase #4	$205.49	4.180%	$214.0795	$214.08	$214.10	$214.10
Purchase #5	$78.85	5.344%	$83.0637	$83.06	$83.05	$83.10
Purchase #6	$74.81	11.163%	$83.161	$83.16	$83.15	$83.20
Purchase #7	$157.47	12.347%	$176.9128	$176.91	$176.90	$176.90
7 purchase totals =	$859.97		$918.9503	$918.93	$918.90	$919.00